In fill-level sensors operating according to the FMCW (frequency modulated continuous wave) method or pulse-transit time method electromagnetic or acoustic waves are emitted in the direction of a feed material surface. Subsequently a sensor records the echo signals reflected by the feed material, the container internals and the container itself, and from them derives the respective fill level.
The book “Radar level measurement—The users guide”, ISBN 0-9538920-O-X, by Peter Devine, VEGA Controls, 2000 describes the basic design of radar fill-level sensors.
The printed publication DE 10 2007 061 574 A1 describes a method for fill-level measuring in which method a reflected component of a signal and a capacitance between a capacitive probe and a reference electrode are measured.
There may be a need to make possible the effective measuring in particular of fill levels and limit levels as well as of characteristics of a feed material.